A variety of diagnostic tests for diseases and other biological conditions which utilize test products featuring built-in, specimen-activated control elements have been described in the patent literature. The purpose, utility and function of these control elements are described in U.S. Pat. Nos. 5,268,146, 5,416,003, 5,585,273, 5,571,684, and 5,660,790. All patents cited in this specification are incorporated herein by reference.
One example of a test product of this type is a self-contained test device designed to detect elevated pH and amines in vaginal fluid specimens (U.S. Pat. No. 5,660,790). The device features built-in, specimen-activated controls with an iconic readout of results. The readout is illustrated by a plus/minus sign, the positive test result being represented by a blue plus sign on a yellow background while the negative test result is represented by a blue minus sign on a yellow background. In this format, the horizontal bar generating the blue color (a yellow-to-blue color change) serves as the positive control while the non-color-changing yellow background serves as the negative control.
Another example is a self-contained test device for detection of proline iminopeptidase (PIP) activity in vaginal fluid, as disclosed in U.S. Pat. Nos. 5,268,146 and 5,571,684, again with built-in, specimen-activated controls. This device consists of a three-dimensional chamber which includes a test zone and positive and negative control zones. A positive test result is indicated by color formation (or change) in the test zone; a negative test result is indicated by the absence of color formation (or change) in the test zone. The positive control should form a color upon addition of a specimen, indicating that the indicator is indeed functioning, whereas the negative control zone should produce no such color, indicating that the device does not produce false positive results.
Products based on reporter enzyme release as described in U.S. Pat. Nos. 5,416,003 and 5,585,273 also feature built-in, specimen-activated positive and negative controls that serve purposes analogous to those of the built-in, specimen-activated positive and negative controls of the test devices of the preceding paragraphs.
The built-in, specimen-activated controls in these devices provide the user with assurance that each individual test device is in proper functioning condition. Because they are built into each device, these controls require no additional steps on the part of the user, and because they are activated by the specimen that is being tested, they can be true controls, ideally suited for this primary purpose.
Nonetheless, at least four additional factors suggest that additional value can be gained by providing dried controls, positive or negative, that are physically distinct from the test devices (i.e., separate devices) and that function independently of the built-in, specimen-activated controls:
(1) Appropriately formulated external controls can allow new users of the test device to see the appearance of a positive test result or a negative test result, prior to using the test device itself with clinical or other specimens, and thereby knowing what to expect or to look for in an actual test;
(2) Appropriately designed controls that are distinct from the test device and do not require specimen activation can provide a training opportunity for new users;
(3) The external controls can be included in a package of test devices, and the user can use the controls upon receipt of the entire package to ascertain that the materials in the test devices have not deteriorated during shipment; and
(4) Physically distinct controls that do not require specimens for activation can permit more widespread use of the test device because they may facilitate regulatory approval for use by relatively untrained personnel.
To meet these objectives, the controls must not only function properly, but they must also be inexpensive and simple to use, and they must have a shelf life at least equal to, and storage requirements no greater than, those of the test device itself. Ideally, for a control device to serve as a training aid, the color produced by the control device should be stable over an extended period of time to permit observation and discussion among trainees. Most currently available external controls usually do not meet these requirements. For example, many current external controls consist of small bottles of positive and negative liquid control reagents that are expensive to manufacture, package, ship and store. Furthermore, such reagents often require refrigeration during storage. To apply liquid external controls to test kits, the user is often instructed to bring the refrigerated control solutions to room temperature before use, and to return them to refrigerated storage immediately after use. These requirements add to the complexity of test procedure. Because of these shortcomings, liquid controls are poorly suited to use with consumer products where instructive assistance is particularly important.
The present invention resides in a control device that is designed for use with any analytical test device, and particularly a solid-phase analytical test device, that is used for analysis of a liquid sample to detect the presence of an analyte in the sample by a detectable change in an indicator in the analytical test device. The control device is distinct from the analytical test device in that no sample is applied to the control device, no chemical reaction occurs in the control device, and no detection is made or test performed in the control device. Instead, the control device merely serves as a source of control reagent(s) to be used in the analytical test device. The control reagent(s) is a dry lamina(e) on the surface of the control device which itself is entirely solid and dry, and the reagent(s) can be removed by a wet swab or other implement and then transferred by the implement to the analytical test device. Once applied to the test device, the control reagent, if it is a positive control, causes a response identical to or analogous to that which would be caused by a sample that contains the analyte, and if the control reagent is a negative control, it causes a response identical or analogous to that which would be caused by a sample that does not contain the analyte. Use of the control device in this manner allows the user to determine whether or not the analytical test device is functioning properly, ie., whether an actual sample in which the analyte of interest is present would itself produce a positive reading on the analytical test device, or whether a sample that did not contain the analyte would produce a negative reading.
The control device of this invention is described herein by the terms xe2x80x9cphysically distinctxe2x80x9d or xe2x80x9cfunctionally distinctxe2x80x9d relative to the analytical test device. These terms are intended to mean that the control device is not functionally joined to the analytical test device, i.e., the mere application of a liquid or a sample to one does not necessarily result in the application of the liquid or sample to the other. The two devices may be on a common base or substrate, and may or may not be separable from each other by cutting the substrate or breaking it along a scored line. Preferably, the two devices are on two distinct substrates that are not connected. In this separated arrangement, the control device is characterized in parts of this specification as xe2x80x9cexternalxe2x80x9d relative to the analytical test device. The control test reagents that are contained in the control device are likewise termed xe2x80x9cexternalxe2x80x9d to distinguish them from built-in specimen-activated control reagents or zones that are part of the analytical test device itself. The control test reagents are also referred to as xe2x80x9cpositivexe2x80x9d and xe2x80x9cnegativexe2x80x9d control reagents. The term xe2x80x9cpositivexe2x80x9d in this context refers to a reagent which, when applied to the analytical test device, produces the same indicator response that would be produced if a sample containing the analyte were applied, the positive control reagent thereby serving to assure that the test device will function properly by producing a positive result when a sample containing the analyte of interest is applied. Likewise, the term xe2x80x9cnegativexe2x80x9d in this context refers to a reagent which, when applied to the analytical test device, produces the same indicator response that a sample that does not contain the analyte is applied, the negative control reagent serving to assure that the test device will function properly when a negative sample is applied.
When the implement used to transfer the control reagent from the control device to the analytical test device is a wet swab, a wet sponge, or any other tool or medium that uses water, the dry positive control reagent is either water-soluble or sufficiently hydrophilic to permit the reagent to be lifted from the control device and transferred to the analytical test device. The control reagent will be chosen for a specific analytical test device, to induce the chemical reaction required in the analytical test device to achieve the indicator change. Depending on the methodology of the test device, the control reagent may therefore be identical, similar, or analogous to the analyte, which may itself be an enzyme, a particular small-molecule chemical species, an antigen or other binding partner, or a species with a high or low pH, for example. Alternatively, the control reagent may be identical, similar, or analogous to a component of the analytical test device that is released or activated by the analyte.
In cases where the control reagent mimics either the analyte or a component of the analytical test device, the control reagent may be the same as the species it is mimicking or a derivative or analog thereof that will function in the same or substantially the same manner. A derivative or analog may be preferable if it is more stable or more compatible with other components of the control device. In the case of a negative control, the control reagent will typically contain all the inert components of the positive control and only those components; i.e., the negative control would not contain the analyte or its analog.
In certain embodiments of the invention, the control device contains two or more control reagents (i.e., all positive control reagents or all negative control reagents), each for a separate test. All such control reagents will be in dry form and all will be transferable by a wet swab or other implement, and yet all will function independently. These embodiments are useful for analytical test devices that contain two or more different tests. In further embodiments of the invention, the dry laminae on the control device containing the control reagent(s) also contain pigments that serve to guide the user by showing where a control reagent is located and whether or not it has already been used. The typical pigment is inert and either accompanies the control reagent as the reagent is transferred or changes color when wetted. The pigmented laminae thus make it easier for the user to locate the laminae on the control device, and provide the user with assurance that the control reagents have been transferred to the swab. The pigments also help the user to differentiate a fresh control device with a full amount of control reagent from one that has already been used and depleted.
In the use of a control device of this invention, control reagent is lifted from the surface of the device and transferred to the analytical test device on which the control test is to be performed. Lifting and transferring is accomplished by any suitable transfer implement, examples of which are a swab, a sponge, a speculum, a pipette, or a dropper. With most of these implements, the reagent is preferably in wet form, i.e., either dissolved or suspended in a liquid solvent, preferably water, to facilitate the transfer. Since the control reagent is a dry lamina on the control device, the solvent can be introduced by the implement itself (a prewetted swab or sponge, or a liquid-filled dropper), or it can be applied first to the control device surface and the resulting liquid lifted from the device by the implement. In either case, the liquid and control reagent are then transferred together to the analytical test device.
These and other features, embodiments, advantages, and uses of the invention are explained in more detail below.
While this invention is susceptible of a wide range of implementations and embodiments, a detailed understanding of the invention as a whole can be gained by descriptions of specific embodiments. Accordingly, this section of the specification will focus on control devices for two particular analytical test devices -an elevated pH and volatile amine test card used for the diagnosis of bacterial vaginosis, as disclosed in U.S. Pat. No. 5,660,790 (Lawrence et al., issued Aug. 26, 1997, xe2x80x9cpH and Amine Test Elementsxe2x80x9d); and a proline iminopeptidase test card for bacterial vaginosis, as disclosed in U.S. Pat. No. 5,571,684 (Lawrence et al., issued Nov. 5, 1996, xe2x80x9cAssay for Proline Iminopeptidase and Other Hydrolytic Activitiesxe2x80x9d).
The elevated pH and volatile amine test card (which will be referred to herein as the xe2x80x9cpH-amine test cardxe2x80x9d) is a laminated device approximately the size of a common consumer credit card and contains two zones on its surface. The first is a pH test zone to detect pH equal to or greater than 4.7, containing an indicator that contains both an ionizable phenol group and a negatively charged group (such as a sulfate or sulfonate group), immobilized in a solid polymer matrix that contains quaternary ammonium groups. An example of an indicator of this description is nitrazine yellow, and illustrative polymers are ammonio methacrylate polymers and copolymers. The indicator and polymer are combined in a proportion that will provide the indicator with a transition point at pH 4.7. This combination of indicator and polymer occupy one geometrically defined surface region of the pH portion of the test card, while a second geometrically defined surface region is occupied by an indicator that has a transition point well below 4.7, for example 4.0 or below or preferably 3.5 or below. An example of an indicator of this type is a combination of nitrazine yellow and bromocresol green. A sample with a pH of less than 4.7 will thus produce a color change in the second region only while a sample with a pH of 4.7 or greater will produce a color change in both regions. If the second region is a bar arranged horizontally and the first region is a bar arranged vertically and crossing the horizontal bar, samples with pH below 4.7 will produce a xe2x80x9cminusxe2x80x9d sign (color change in the second region only) while sample with pH 4.7 or above will produce a xe2x80x9cplusxe2x80x9d sign (color change in both the first and second regions). An external negative control reagent in accordance with this invention will likewise produce the xe2x80x9cminusxe2x80x9d sign when applied to the pH portion of the test card, and an external positive control reagent will produce the xe2x80x9cplusxe2x80x9d sign.
The second test zone on the pH-amine test card is a test zone to detect the presence of volatilizable amines in the sample. The zone contains an indicator such as bromocresol green in a gas-permeable but liquid-impermeable matrix such as ethyl cellulose, plus a gaseous amine-releasing agent such as a solid alkali (sodium aluminate, for example). Thus, only those amines in the sample that are volatilized upon contact with the gaseous amine-releasing agent are able to produce a change in the indicator since only the gaseous amines can penetrate the matrix. This matrix occupies one geometrically defined region on the surface of the amine test portion of the card, while a second geometrically defined region is occupied by a different matrix, i.e., one that is both gas-permeable and liquid-permeable. Hydrophilic polymers, such as those used as matrices in the pH portion of the test card, will meet this description. The indicator in the second region can be the same as that used in the first region, and can be activated either by volatile or non-volatile amines or by the alkali used as the gaseous amine-releasing agent. As in the pH test, the second region can be a bar arranged horizontally while the first region is a bar arranged vertically and crossing the horizontal bar. A sample that does not contain amines that will be volatilized upon contact with sodium aluminate will produce a xe2x80x9cminusxe2x80x9d sign (color change in the second region only) while sample that does contain volatilizable amines will produce a xe2x80x9cplusxe2x80x9d sign (color change in both the first and second regions). An external negative control reagent in accordance with this invention will likewise produce the xe2x80x9cminusxe2x80x9d sign when applied to the amine portion of the test card, and an external positive control reagent will produce the xe2x80x9cplusxe2x80x9d sign.
The external positive and negative controls in accordance with this invention are not to be confused with the internal positive and negative controls that are included in the test device itself. As explained in U.S. Pat. No. 5,660,790, the internal positive and negative controls generally operate in a different manner, showing in an indirect way that the reagents are functioning but doing so without producing the same visual indication as a positive and a negative test result. By contrast with such internal controls, the external controls of the present invention mimic the positive and negative results in the test device by producing the same visual indication (for example, a plus sign for the positive result and a minus sign for the negative).
A preferred control device in accordance with this invention for the pH-amine test card is a single dried external positive or negative control device for testing both test elements of the pH-amine test card (i.e., controls for both the pH and amine test elements). The user simply rubs a wet swab over the dried control reagents, either individually or together, and performs the pH-amine test card tests according to the standard clinical instructions for using the pH-amine test card. The test result for each test element is preferably a color development which develops rapidly to intermediate intensity in both tests and is readily interpreted by novice users, the positive control producing a visual indication of a positive result (such as a plus sign) and the negative control producing a visual indication of a negative result (such as a minus sign). The control device should be as simple as possible to use and its effectiveness should be independent of the technique of the individual user.
For the pH test, an appropriate external positive control reagent will be any dried reagent that produces a pH substantially above 4.7, and preferably 5.0 or above, on the transfer implement used to transfer the reagent from the control device to the test card. In most cases, this will be a soluble acid, base or neutral species, optionally combined with an appropriate buffering agent. Examples of appropriate acids are 2-(N-morpholino)ethanesulfonic acid and citric acid, in solid, dry form. An appropriate external negative control will be any dried reagent that produces a pH substantially below 4.7 on the transfer implement. This reagent will in most cases be a soluble acid, optionally combined with an appropriate buffering agent, preferably one that maintains a pH less than 4.0, and most preferably less than 3.5. Other components that are preferably included in the positive control are a film forming agent to assist in the application of the control as a secure solid film to the surface of the control device, one or more detergents to enhance the wettability of the transfer implement with the control material and hence the ease of picking up the control by the implement and transferring it to the test device, and optionally other such components included for their physical properties but otherwise inert.
For the amine test, an appropriate external positive control will be any dried species that can be transferred by the transfer implement and that produces a volatile unprotonated amine when placed in contact with the gaseous amine-releasing agent on the test card. Examples of amines that meet this description are acid salts of primary amines, such as methylamine and diaminobutane. Likewise, an appropriate negative control will be any dried species that does not produce a volatile amine under the same circumstances. Like the other controls, the negative control may include a buffering agent, and may also include film formers, detergents, and other components to enhance the ability of the control reagent to form a film on the surface of the control device and to enhance the ability of the transfer implement to pick up the control and transfer it to the test device.
The preparation of dried control reagents or reagent laminae that are capable of meeting these performance goals and that meet the stability requirements and ease-of-use needs of the marketplace is accomplished by using materials with an appropriate balance of chemical properties. When an amine is used as the amine test positive control reagent, the amine control in its dry form on the control device should be maintained at a low pH to prevent oxidation and/or volatilization of the amine upon storage. This can be accomplished by using an acid salt of the amine. If the acid salt is present in excess, however, its acid content can partially or completely neutralize the alkali ring (the gaseous amine-releasing agent) surrounding the amine test element of the pH-amine test card, thereby interfering with the generation of the free, unprotonated amines that produce the color change in the amine test element. Conversely, the positive control reagent for the pH test should have a pH well above 4.7, and preferably in the range of approximately 5.0 to 7.0, to ensure credible, rapid color development in the pH test element on the pH-amine test card. Conversely, it has been found that high ionic strength is detrimental to color development of the pH element. Hence, preferred pH positive control reagents are those having a reasonably low ionic strength.
In embodiments of the invention in which the positive control reagents for both the pH test and the amine test are transferred simultaneously by the transfer implement and thus in contact on the implement, the two reagents should be formulated to eliminate or at least minimize any neutralizing or deactivating effect that either one may have on the other. For example, the amine test positive control reagent may be formulated to include a small amount of buffering agent to assure that when this reagent is combined with the pH test positive control reagent, the resulting pH is high enough to produce the positive result when applied to the pH portion of the test card. Likewise, if the combined positive control reagents have a pH that is too high, the amine components may deteriorate; whereas if the pH is too low (to stabilize the amine components), the pH control reagent may not produce a positive pH test result. Similarly, if the combined ionic strength of the two components is too high, the pH control may not function as desired, despite the pH of the formulation. These considerations will affect both the formulations of the control reagents and the choice of the manner in which they are arranged on the surface of the control device. In some cases, these considerations can be ameliorated by appropriate choice and combination of components for each formulation, and in other cases by selecting a geometrical or physical arrangement that will reduce the possibility of mixing or contact of the reagents before they are gathered by or absorbed into the transfer implement.
A preferred control device is one that contains dried, stable, functional positive controls for both test elements of the pH-amine test card, arranged in such a manner that both are picked up simultaneously by a single swab or other transfer implement and then both are applied simultaneously by the implement to first one test zone on the test card and then the other. This can be accomplished by placing all components for both pH and amine test elements in a single control reagent lamina or by placing them in individual, geometrically separated pH and amine control reagent laminae, zones or areas that are positioned sufficiently close to each other to permit the user to apply the transfer implement to all of the reagents substantially at the same time. Alternatively, the control test device can contain two independent dried external controls (ie., separate pH and amine controls, both positive or both negative) on separate locations of the device to be removed separately.
Single, combined reagent formats in the form of one or more identical, superimposed control reagent laminae, each containing all components needed to produce a positive response on both the pH and amine test elements, can thus be prepared. To perform the control test, the user rubs a wet swab over a designated area on the device, thereby transferring the control reagents which were deposited on that area to the swab. The swab is then used to apply the combined control reagents to both test elements (pH and amine) of the test card. Alternatively, the user can wet the control reagent area first and then rub a dry swab over the wet surface to pick up the control reagents. The single combined reagent (single lamina) approach has the advantage of simple manufacturing, but may in some cases (for the reasons given above) present challenges in formulating the reagent combination and in achieving long term stability if the individual control reagents have conflicting requirements.
A multiple laminar format, i.e., one in which individual controls are placed in separate and discrete laminae on the surface of the control device, can be prepared by using vertically or laterally separated laminae. In the pH and amine test example, the positive pH control reagent laminae may thus be placed in one lamina and the positive amine control reagent in another lamina. The term xe2x80x9cvertically separatedxe2x80x9d or xe2x80x9cvertically arrangedxe2x80x9d denotes distinct but superimposed laminae, one applied over the other, on the surface of the control device which is held in the horizontal position. The term xe2x80x9claterally separatedxe2x80x9d or xe2x80x9claterally arrangedxe2x80x9d denotes laminae or regions that are placed side-by-side in a non overlapping manner, and preferably separated by a small gap, on the surface of the device. One example of a geometric pattern of laterally separated laminae or regions is two halves of a circle in which one half is occupied by the pH positive control reagent and the other by the amine positive control reagent. Another example is a circle divided into quarter sections, where one of the two pairs of diagonally arranged sections is occupied by the pH positive control reagent and the other by the amine positive control reagent. A third example is two or more concentric rings where adjacent rings alternate in the control reagent occupying them. A fourth example is parallel strips where adjacent strips alternate between the pH control reagent and the amine control reagent. Other arrangements will be readily apparent to those skilled in the art.
To use the control device, the user mixes the laminae together with a wet clinical swab or other implement immediately prior to application to the test card to perform the control test. In the vertically separated arrangement the user rubs the swab over the uppermost lamina, drawing reagent from both laminae simultaneously. In the laterally separated arrangement, the user rubs the swab over the various regions using a circular or lateral sweeping motion, contacting each region. In either the vertical or lateral separation, both control reagents are mixed and picked up by the swab, then transferred to the pH-amine test card to perform control tests on the two test areas in succession. While these multiple laminar arrangements entail somewhat greater manufacturing complexity than a single laminar arrangement, they avoid the difficulties of incompatible control reagents and offer the potential benefit of utilizing two readily formulated reagents which interact minimally with each other until mixed by means of the swab.
Turing now to another example, the proline iminopeptidase (xe2x80x9cPIPxe2x80x9d) test card is also a laminated device approximately the size of a common consumer credit card, the laminae forming an internal chamber with two opposing but non-contacting surfaces, one surface containing the conjugate L-proline-xcex2-naphthylamide and the other containing the chromogenic indicator Fast Garnet GBC. When a sample containing proline iminopeptidase is placed in the chamber, the proline iminopeptidase cleaves the conjugate to release xcex2-naphthylamine which migrates toward the indicator and changes its color. Referring to this chamber as the central chamber, the test card also contains two lateral chambers, one of which produces the same color change as the central chamber but does so regardless of whether or not the sample contains proline iminopeptidase. This is achieved by placing a solid non-volatile naphthylamine in the lateral chamber rather than the L-proline-xcex2-naphthylamide, but also including the same indicator in the lateral chamber, the solid non-volatile naphthylamine being one that will dissolve in the sample and react with the indicator to produce the color change. An example of a naphthylamine meeting this description is 3-amino-2-naphthoic acid. Although the central and lateral chambers are joined by channels to permit the sample to enter both, the reagents remain in the respective chambers to differentiate the locations of the color changes.
A dried external positive control reagent in accordance with this invention for the PIP test card in accordance with this invention is preferably one that will contain the xcex2-naphthylamine (or a similarly acting analog) in a form that is readily transferable by the transfer implement and once transferred will produce the indicator change in the central chamber, and yet prior to use will remain in dried form on the control device for an extended period of time until needed. xcex2-Naphthylamine itself is volatile and slowly vaporizes. The positive control reagent should therefore be a naphthylamine derivative that remains firmly restrained within the dried control lamina until dissolved by a solvent (on a swab or other implement) and yet produces the color change in the indicator once it is dissolved and transferred. An example of such a derivative is a charged sodium salt of 3-amino-2-naphthoic acid. A lamina matrix that will stably retain this derivative is a quaternary amine polymer such as quaternized vinylpyrrolidone/dimethylaminoethyl methacrylate copolymer (GAFQUAT(copyright) 734, ISP Technologies, Inc., Bound Brook, N.J., USA) which holds the reagent within the lamina by ionic attraction. For a negative control, the lamina will contain only the quaternary amine polymer, plus any other components that may be included in the positive control other than the naphthylamine derivative.
As exemplified by the PIP test, some of the negative controls in accordance with this invention will not require a special reagent but instead simply the absence of the analyte or its analog to produce a negative indication on the test device. These negative controls should still be specially formulated to include all or substantially all of the reagents of the positive control other than the analyte or analyte analog, to assure a consistent and reliable result. For example, where water alone could produce the negative indication in the test device, a properly formulated negative control avoids the disadvantages of the variable ion composition, ionic strength and pH of tap water, while offering the advantage of the same consistency, appearance and procedure of use of the positive control. Thus, the negative control may contain buffering agents, film forming agents, and detergents, where these components are also present in the positive control. These components will therefore serve as the negative control reagent.
Whether the control device is designed for use on a pH-amine test card, a PIP test card, or on any other type of analytical test device, and whether the control reagents on the control device are single laminae or multiple laminae, vertically separated or laterally separated, certain additional features will often be useful. For example, when the control reagent laminae are colorless or nearly colorless, the user may find it useful if some means is provided to make the control reagent laminae readily visible on the control test device, the swab, or both.
One means of achieving this is to use a control device whose underlying base is strongly colored and/or shiny. The control reagent laminae can be made to appear as semi-opaque or to have a milky appearance, and its removal from the shiny, colored surface of the device will be readily apparent.
Another means of making the control reagent(s) visible is to incorporate an inert dye or pigment into the control zone. The colored area thus shows the user where to apply the swab (or other implement). The user can also determine whether the reagent has been picked up by the implement by examining the surface of the device for removal of the colored area or by examining the implement itself. Laminar pigmentation can be achieved by adding a dye or pigment to one or more of the reagent laminae, or by depositing one or more chemically inert dye or pigment laminae beneath or above the control reagent laminae. A further means of making the control reagent(s) visible and confirming whether or not they have been used is to use colored laminae that change color upon contact with the transfer solvent. This can be accomplished with a suitable pH indicator. The dyes, pigments, or other coloring agents can be chosen and tested specifically to assure that they will present no interference with the control reagents themselves. The quantities and color of the dyes, pigments, or coloring agents would also be chosen to assure that there will be no interference with the color change in the test zone on the analytical test device, and to have no effect on reagent stability.
An alternative to the use of dyes, pigments, or coloring agents is the incorporation of highly colored polymeric microparticles into one or more control reagent laminae or into a top or bottom lamina (i.e., above or below the control reagent). Microparticies with coloring agent imbedded inside them during their formation are known in the art. The coloring agent in these microparticles will not directly contact the control reagents, even when both are retained on a single swab. These microparticles are highly inert and tend to adhere to clinical swabs, thereby transferring little or no color to the analytical test device.
Regardless of their configuration or chemistry, the control test devices of this invention will generally contain indicia such as drawings, illustrations, or text, instructing the user as to the appropriate methods of use.
In manufacturing a control test device in accordance with this invention, the control reagent(s) is applied to a solid base or support in a conventional manner to form a lamina or laminae on the surface of the base. When there are constraints on the concentration of the reagent in the formulation being applied, it may be necessary to apply multiple laminae superimposed to achieve the desired amount of reagent. When laterally separated laminae are applied, the geometric patterns can vary considerably and are not critical. For example, distinct reagents can be applied side-by-side as two halves of a circle, as a series of concentric rings, or as alternating strips. When vertically arranged (superimposed) laminae are applied, particularly when one lamina contains a different control reagent than the one directly above or below it, one can avoid mixing of the reagents during formation of the laminae by using different, incompatible or immiscible solvents for the formulations used to form each lamina. Combinations of laterally and vertically separated laminae can also be used.